The present invention concerns tuning apparatus for antennas which receive broadcast signals such as television signals.
Conventional indoor TV antenna systems generally include two separate antennas for respective VHF and UHF reception. The antenna for receiving the VHF bands employs a pair of telescopic elements forming a dipole with each of the elements having a maximum length of from 4 to 6 feet (1.5 to 2.5 m). The two elements usually are mounted to permit the elements to be spread apart to increase or shorten the dipole length and those elements are commonly referred to as xe2x80x9crabbit ears.xe2x80x9d The indoor UHF antenna typically is a loop having a diameter of about 7xc2xd inches (20 cm).
One problem associated with the conventional indoor antenna systems is that the physical dimension of the VHF dipole is undesirably long for the ordinary setting in a living room and that the length as well as the direction of the dipole elements may need to be adjusted depending upon the receiving channels. The second problem is that the performance of such conventional indoor VHF/UHF antennas changes in response to changes of the physical conditions around the antenna elements. For example, it is difficult for a user to make proper adjustment of the antennas since a human body coming into contact with an antenna changes the electro-magnetic conditions associated with the antenna elements. The third problem is that the conventional indoor antenna systems do not always provide a sufficient signal level for good reception.
A need exists for an antenna system including compact-size antennas which are capable of receiving a sufficient level of signals throughout the entire VHF/UHF broadcast bands of frequencies without any physical adjustments. Further, there is need for such an antenna system that can be used in either indoor or outdoor applications.
In accordance with the present invention, a tuning apparatus for VHF/UHF signals comprises an automatic gain control (AGC) arrangement including an amplifier for controlling the gain of the amplifier and a plurality of impedance matching networks coupled between an input and the amplifier. Each one of the plurality of matching networks exclusively provides the AGC arrangement with a respective group of RF signals which includes a plurality of receivable broadcast channels. The gain of the amplifier is controlled in response to the level of the group of RF signals.
Another aspect of the invention is as follows: In an antenna system for providing VHF/UHF signals for a receiver, the receiver which has a remote control transmitter for generating control signals for selecting individual ones of the VHF/UHF signals corresponding to respective broadcast channels, apparatus comprises (1) a plurality of matching networks coupled between an input to which an antenna may be coupled and an output circuit for providing impedance matching between the antenna and the output circuit where each one of the plurality of matching networks exclusively provides the output circuit with a respective group of RF signals which includes a plurality of receivable broadcast channels and (2) control means coupled to the plurality of matching networks and responsive to the control signals generated by the remote control transmitter for selecting the individual ones of the VHF/UHF signals corresponding to respective channels for selecting ones of the plurality of matching networks.